After racking up a 5-1 record prior to joining the UFC—the lone loss coming by way of DQ—Tom Lawlor was invited to join The Ultimate Fighter 8 light heavyweight tournament. Although he was knocked out and forced out of the competition by eventual winner Ryan Bader, Lawlor made a name for himself with his prank-pulling antics and a charismatic persona.

Following his stint on the show, Lawlor earned back-to-back UFC wins, including a $100,000 Submission of the Night performance against CB Dollaway at UFC 100. After his 2-0 UFC start, Filthy would lose his next next two fights to Aaron Simpson and Joe Doerkson. Lawlor has since gone 2-2, with his most recent loss coming to Francis Carmont at UFC 154 in Montreal, Quebec, Canada, via split decision.

While he has been inconsistent inside of the Octagon since joining the UFC, Lawlor is always a contender for a post-event bonus and is known for his exotic and sometimes over-the-top weigh-in outfits and ring entrances. In his UFC 113 fight with Joe Doerksen, Lawlor came in dressed as UFC Hall of Famer Dan Severn and has even come into a weigh in disguised as the "Just Bleed" man.